Render Rate


Apple’s Mail Privacy Protection Initiative which is included with iOS 15 and is expected sometime in the fall of 2021 will impact Open Rate, Click-to-Open Rate, Open Reach Rate, and Render Rate for users reading mail on Apple Mail. The information here may change and we will update it when we know more. To learn more visit the Only Influencers Pixelgeddon Resources Page.

Render Rate is a value between 0 to 1 expressed as a percentage between 0% and 100%.

What is the render rate? The number of times that an email is displayed (whether fully opened or within the preview pane) and recorded using tracking pixel. If a user opens the email multiple times or multiple tracking pixels requests are recorded due to forwarding, only one is counted per unique email address. This metric applies to HTML formatted emails only.

The render rate differs from the open rate in that it only applies to HTML emails and is only counted when the tracking pixel fires. While a regular open is determined by counting either when the pixel fires or if clicks occur without images downloading. The Render Rate can be calculated using the unique or total number of email renders. 

The term “Render Rate” was invented by Loren McDonald while he was volunteering with the SAME Project, circa 2008. David Daniels was original founder of EMAC – Email Measurement Accuracy Coalition that became the SAME Project once it was merged with the eec.

At the time of the SAME Project, during the late 2000s, image blocking was much more prevalent than today. Most of the most popular email clients still blocked images by default, including all versions of Gmail, Outlook, and most other clients. Smart Phones started to allow HTML emails at this time, but often it was simply markup such as bold or italics and links for basically a plain text email. So, at the time, there was a real difference in Render rates vs. Open rates, which has largely disappeared today.  

While image blocking is not the issue that it was in email’s early days, the Render Rate and counting email renders still has a value. Email Renders, measured purely by pixel hits, are the same form of image tracking used for regular display and PPC ads, so Email Renders are the same as impressions in other digital advertising. Using this form of opens measurement works for accurate cross-channel comparison. For example, a Render-based Click to Open rate would be mathematically equivalent to another digital ad’s CTR.   

Restricting your sample to those that fired the pixel or unique email renders is a good way to control for creative testing. This limits your sample to only those that saw the fully displayed email creative, using traditional metrics like Click to Open and CTR, may introduce responses that came from plain text versions or people viewing without downloading images. When the test imagery, you want to have way to control variances produced by those edge cases. While image blocking is no longer a problem, we are seeing the rise of email readers that use the plain text version as well as plain text versions being displayed in wearables.  One example, would be a device like the Apple Watch often shows plain text versions of the email. This means there can be and probably are clicks and other activity from subscribers than using plain text versions. I still see clicks from plain text versions in my ESP reporting and still send Plain Text versions, though now it is more for accessibility than dealing with restricted email clients that were still around when I started my career.

Related Links:

Sparkpost “New Feature: Initial Renders Metric for Better Engagement Tracking“ 2017: 

eec Measurement Accuracy Board “SAME Project Metrics Definitions”, Email Experience Council, 2010:

eec Measurement Accuracy Board “‘A Call to Action for Standard Email Metrics”, Email Experience Council, 2010: 

MAPP “eec – Email Experience Council”, 2010

Read Rate (deliverability) - The Email Metrics Project

Read Rate (deliverability) - The Email Metrics Project

[…] shows the percentage of people that downloaded the pixel image out of delivered email (see Open or Render Rates).  Open rates tell you how many people in your list opened (and presumably read) the email, […]

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